1. Field of the Invention
The present invention relates a method for separating mixtures of gases, vapors or liquids by diffusion through membranes. This method is intended to separate atoms and molecules of various types from one another.
2. Description of the Background
In the past, molecular separations of this type have been effected by distillation, ultracentrifugation, precipitation, separation in chromatographic columns or diffusion through membranes. These known methods are relatively expensive due to high energy requirements, and some are not very specific, i.e., the separation process must be repeated in many successive stages, as very little enrichment is realized in each stage. Moreover, in processes such as distillation or precipitation, chemical changes occur in the substances to be separated.
Very few materials are available for separation by diffusion through membranes. In addition, a drawback of all known membrane separation processes is the great variation of pore sizes within the membranes.
The membranes and nuclear trace filters which are produced by subjecting a matrix to high energy radiation to form nuclear traces, and then subjecting the matrix to an etching process are known. The nuclear traces are etched to become holes whose diameters begin at about 5 nm (50 .ANG.). These nuclear trace filters are used for ultrafine filtering of particles; it is, of course, not possible to use them to separate mixtures of atoms or molecules that all have molecular diameters significantly below the above-stated range.